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Mobile Acoustic Sampling to Map Bathymetry and Quantify the Densities and Distributions of Salmonid Smolt Predators in the San Joaquin River
| 题名： | Mobile Acoustic Sampling to Map Bathymetry and Quantify the Densities and Distributions of Salmonid Smolt Predators in the San Joaquin River |
| 作者： | Cutter, G. R.; Manugian, S. C.; Renfree, J.; Smith, J.; Michel, C.; Huff, D.; Sessions, T. S.; Elliot, B. E.; Stierhoff, K.; Mau, S.; Murfin, D.; Demer, D. A. |
| 关键词： | Mobile Acoustic Sampling##Map Bathymetry##Salmonid habitat##Smolt migration##Quantifying##Densities##Distributions functions##San Joaquin River Basin California##Habitats (Ecology)##Backscatter analysis##Fish densities##Abundances##Morphology (Biology)##Sacramento-San Joaquin River (SJR) system## |
| 摘要： | Salmon smolt mortality in the Sacramento-San Joaquin River (SJR) system of central California is impacted by predatory fish. To quantify the abundance, distribution, and habitats of these predators, we devised and implemented novel active-acoustic methods to sample the fish and bathymetry in this shallow-water environment. Acoustic surveys using vertically- and horizontally-oriented split-beam and multibeam sonars were conducted between March and May, 2014 and 2015, from the Port of Stockton to Lathrop, California. Individual fish were acoustically detected using single-target detection and echo-track processing methods, and aggregated fish counts were converted to densities and abundances by compensating for the sampled volumes of the acoustic beams, the probability of target detections, and the river volume. Volume was estimated from 1-by-1- m grid-cell bathymetric maps produced from M3 multi-beam sonars for the 26-km study area. Bathymetric mapping and target detection efforts were complicated by the low grazing angles, high-reverberation and clutter, and strong second bottom returns induced by the shallow river environment. Riverbed habitats were discriminated by morphology and back-scatter intensity, and bathymetry data were used to constrain sonar detections of fish. Additionally, novel signal processing of M3 water-column data was used to map submerged aquatic vegetation (SAV) beds and to detect fish among clutter. Predators were associated with certain riverbed features and SAV along the part of the route that salmon smolt migrate to the ocean. Fish densities were highly variable in both space and time, however, persistently high densities occurred in many deep pools in the bends of the river. |
| 总页数： | 137 |
| 报告类型： | 科技报告 |
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